This work is aimed at determining the mechanisms by which electrolytes and water are secreted by the exocrine pancreas. Micro-pH and PCO2 electrodes as well as micropuncture and microperfusion techniques are being used to measure ionic composition of the ductal contents at various points along the ductal system. This work is being conducted in the anesthetized rabbit. Studies are also being conducted on the pancreas of the chronically reserpinized rabbit. This produces a pancreatic secretion which resembles that seen in human patients with cystic fibrosis. The goal of these studies is to deduce the nature of the pancreatic lesion in cystic fibrosis.